Catalytic conversion of hydrocarbons



Aug. 17, 1954 J. w. JEWELL CATALYTIC CONVERSION oF HYDRocARBoNs FiledJune l, 1951 INVENTOR. JOSEPH W. JEWELL ayfaffpemf ATTORNEYS PatentedAug. 17, 1954 CATALYTIC CONVERSION OF f HYDROCARBONS Joseph W. Jewell,Summit, N. J., assigner to The M. W. Kellogg Company, Jersey City, N.J., a corporation of Delaware Original application July 7, 1945, SerialNo.

603,668. Divided and this application .lune 1, 1951, Serial No. 229,458

1 This application is a division of copending application Serial No.603,668, iiled July 7, 1945` now abandoned. Serial No. 603,668 was acontinuation-in-part of application Serial No. 405,614, filed August 6,1941 now U. S. Patent 2,385,446. The claims of the present applicationare directed to specific features disclosed but not claimed in saidparent applications.

The present invention relates to improvements and practiced inrelatively inexpensive equipment.

` Various other objects, advantages and features ci the invention willbe apparent from the following detailed description thereof given inconnection with the appended drawing wherein the gure is a diagrammaticillustration of a suitable arrangement of apparatus and process flow forthe prac* tice of the invention as applied to the catalytic conversionof high boiling hydrocarbons such as in process and apparatus foreffecting catalytic lo petroleum gas oil, or the like, to low boilinghydroconversions. In its specic aspects, the invencarbons. tion isdirected particularly to an improved con- The principal units of theapparatus illustrated tinuous process of converting hydrocarbons by are:a heater l for supplying vaporized hydrotreatment over catalyticmaterials which become carbons at a temperature suitable for conversion,spent or deactivated during the conversion by l5 a reactor or conversionchamber 2 wherein partithe accumulation of carbonaceous materialtherecles of catalytic cracking material are contacted on, and whichaccordingly reduire periodic re- With the feed vapors undergoingcracking, a regeneration treatment to fit them for reuse in thegeneration vessel or regenerator 3 wherein the conversion step. Thecatalytic conversion of high particles of used or spent catalyticmaterial are boiling hydrocarbons such as petroleum gas oil contactedwith an oxygen-containing gas under and the like into low boilinghydrocarbons within conditions adapted to cause combustion of the thegasoline boiling range is an example of the carbonaceous depositthereon, a blower Il or other latter type of conversion reaction ofoutstanding suitable means for supplying an oxygen-containimportance,ing gas, such as air, to the regenerator, and gas- It has been proposed,heretofore, to catalytisolid separating means 5 and t associatedrespeccally convert high` boiling hydrocarbons such as tively with thereactor and regenerator for sepagas oil to low boiling hydrocarbonsWithin the rating suspended particles from the effluent gases gasolineboiling range by passing vapors of the derived therefrom. high boilinghydrocarbons under suitable reac- Pursuant to the present invention, arelatively tion conditions in contact with a stationary bed denseconcentrated phase or mass of `catalytic of a cracking catalyst disposedin a catalyst particles is formed in the conversion zone or rechamber.Pursuant to such processes, after the generation zone, or preferablyboth, and moved activity of the catalyst is decreased by reason oflaterally in contact with the vaporous or gaseous the formation of acarbonaceous deposit thereon component which travels upwardly throughthe to an extent where regeneration is necessary or laterally movingCatalyst at a relatively low Vedesirable, the activity of the catalystis restored locity, The conversion zone and regeneration by stopping theflow oi oil vapor tothe chamber Zone preferably are constituted byhorizontally and passing an oxygen-containing gas `into the elongatedvessels of relatively great length comchamber in contact with the spentcatalyst, therepared to their width and depth, or diameter in byregenerating it in situ by combustion of the the case of cylindricalvessels. Catalytic particles carbonaceous deposit. Although suchprocesses undergoing contact with the vaporous or gaseous arecommercially practicable they are subject to component are supplied atone end portion of the a number of inherent limitations and disadvanelongated vessel and withdrawn at the opposite tages which areeliminated by the present inend portion. In the case of the conversionzone, vention. Among these are the intermittent the rate of addition ofthe fresh or regenerated nature of the" operation, variations in productcatalyst particles thereto and the corresponding quality and quantityduring the reaction period rate of withdrawal is such as to maintain theand difficulty in temperature control, particularly laterally movingdense mass at the desired average in the regeneration operation. degreeor level of catalytic activity. In the case A primary object of myinvention is the proof the regeneration zone, used or spent catalyticvision of a continuous process of eiecting the particles are addedthereto and withdrawn at catalytic conversion of hydrocarbons andanalosuch a rate that the catalytic particles will regous reactions,wherein the mentioned disadvanmain in this zone for the period of timerequired tages of the intermittent type of operation are to eliminate orreduce the carbonaceous deposit obviated, and which may readily becontrolled tothe desired extent. The vaporous or gaseous component issupplied at such a rate that its upward velocity through thee onversionand regeneration zone is adapted to maintain the mass of catalystparticles therein in a readily fiowable but relatively dense state. Thiscondition of the mass of catalyst particles is such that it resembles aliquid in its flow characteristics and the aerated mass of catalyst inthe intermediate portion of the zone is accordingly displaced and causedto flow laterally by the addition of catalytic particles at one end ofthe zone and withdrawal of corresponding amounts at the opposite end ofthe zone.

Following now the typical process ow illustrated by the drawing, thefeed to the process for example a petroleum gas oil, or a similar highboiling hydrocarbon fraction, is introduced through line 2 to heatingcoil 3' in furnace I wherein it is vaporized and heated to a temperaturesuitable for the subsequent conversion operation. From furnace I thefeed vapors are passed by transfer line 4 to a suitable vapordistributing means such as manifold 5. From manifold 5' a plurality ofbranch valved feed lines 6' connect with the lower portion of reactor 2.The quantity of feed vapors introduced through each of the branch linesmay be suitably independently regulated by the individual valves 8.Lines 6 and lines 2l preferably terminate in suitable distributing meanssuch as a perforated spider or porous plates (not shown) to providesubstantial uniform horizontal distribution of the vapor throughout theconversion zone.

Particles of a suitable catalytic cracking material, for example anactivated clay such as Super-Filtrol in finely divided or powderedcondition is supplied at one end portion of reactor 2 through thecatalyst inlet conduit 1. Reactor 2, as shown, consists of a cylindricalvessel of relatively great length, or elongated horizontally relative toits diameter. Fresh catalyst may be supplied through inlet l, but innormal operation this catalyst will consist largely of previouslyregenerated hot catalyst withdrawn from regenerator 3 through line 9.From line 9 the regenerated catalyst is picked up by a stream of asuitable conveying fluid such as steam injected through line II andconveyed through transfer line I0 to the catalyst inlet 'I. The quantityof the conveying uid employed and the relative cross-sectional area ofthe transfer line IB compared to the corresponding area of reactor 2 aresuch that the catalyst particles drop out of the stream of conveyingfluid into the reactor. This separation may be facilitated by a baiTleI2 disposed across the path of the flowing mixture of conveying fluidand catalyst particles introduced through inlet 1.

Vapors of the hydrocarbons undergoing treatment are admitted throughlines 6 at the base of reactor 2 in .such quantity that the mass ofcatalyst particles, the upper level of which is indicated by dotted lineI3, is maintained in a readily flowable but relatively concentrated ordense condition.r In this state the mass of particles assumes acondition resembling that of a liquid in its ow characteristics, and iscaused to flow or be positively displaced laterally through the reactorby the addition of active or regenerated catalyst at one end portion ofthe reaction zone through inlet 'I and the withdrawal of used or spentcatalyst from the opposite end portion of the reaction zone through theloWer catalyst outlet I4 which communicates directly with the densecatalyst phase. The height of the upper level I3 of the dense catalystphase is dependent upon the total quantity of catalyst in the system andthe rate at which catalyst is withdrawn through the lower catalystoutlet III, which rate is controlled by valve I5. Accordingly, level I3may be maintained at any desired height by suitable control of the rateof withdrawal of catalyst through valve I5 and regulation of the totalamount of catalyst contained in the system. The latter regulation may beaccomplished by either adding catalyst from make up catalyst hopper I6to the system or by withdrawing a quantity of circulated catalyst tostorage as required. The level I3 is preferably maintained a substantialdistance below vapor outlets Il, most suitably in the lower half of thereactor as indicated, in order to provide an ample catalyst-vapordisengaging space in the reaction zone above the dense catalyst phase.Under such conditions a relatively small portion of the circulatedcatalyst is carried out of the reaction zone by the vaporous reactionproducts withdrawn overhead from the reactor through outlet lines Il'.Other conditions being fixed, the quantity of solid particles carriedout with the vapors through lines I'I is dependent upon the height oflevel I3. For example, if valve I5 was completely closed level I3 wouldrise to an extreme limit where solid particles would be carried outthrough vapor lines II at the same rate as added through inlet l.Conversely, by progressively increasing the 'distance between the vaporoutlet and the level, the quantity of solid particles carried outoverhead is progressively decreased to a lower limiting value. Pursuantto the present process, it is greatly preferred to maintain suchconditions that only a relatively small quantity of solid particles iscarried out with the efliuent gaseous component since the equipment forrecovering of such material from the gaseous component is therebygreatly simpliiied and reduced in cost.

From outlet lines II vaporous reaction products are passed by manifoldI'I and line I8 to suitable means for recovering the residual quantityof catalyst particles remaining therein and thereafter to suitablerecovery means for condensation and separation into the desiredproducts.

From manifold I'I' the vaporous reaction products may be passed by lineI8 to a suitable gassolids separating equipment, such as cyclones or thelike, indicated diagrammatically by the numeral E. From separator 6 thevaporous reaction products are passed by line I9 to a fractionator orsimilar apparatus of conventional design and hence not illustrated.Separated residual catalyst withdrawn from separator 6 may suitably bereturned to the catalyst stripping Zone 2li in reactor 2 by catalystreturn line 2 I After passing in contact with the hydrocarbon yapors,the uid mass of spent catalyst particles is preferably subjected to astripping operation .to remove adsorbed or entrained hydrocarbon vaporstherefrom prior to the passage of these particles to the regenerationstage. This strip- .ping operation may suitably be effected in adistinct stripping zone 2l) within the reactor and ,defined by the spacebetween the end of the reactor and baffle 2l. A suitable aerating andstripping medium such as steam is supplied to the lower portion of thisstripping zone by line 22 to a steam ring or other suitable distributingmeansv 23 disposed in the lower portion of the stripping zone. Thestripping medium is supplied in such quantities that it passes throughping medium andstrippedvapors may suitably be withdrawn overhead fromthe stripping zone through line 24 and combined with the vaporousreaction products in line I8.

Spent catalyst may be suitably' withdrawn from the base of the reactorthrough a valved catalyst standpipe 25.` Standpipe 25 is preferablyprovided with an enlarged portion I4 at the upper end thereof to whichan aerating and stripping medium may be introduced through line 26 anddistributors 29' for the purpose of maintaining the withdrawn catalystin a readily flowable condition and also to effect additional strippingaction. Additional aerating fluid is preferably introduced at suitablyspaced points along the length of standpipe 25 through lines 28 tomaintain the catalyst therein'.` in a readily ilowable condition. i

As illustrative of suitable operating conditions in the practice of theinvention as applied to the catalytic conversion of a petroleum gas oilfeed stock to low boiling hydrocarbons within the motor fuel boilingrange, there is given in the following Table A suitable conditions forsuch a unit `based upon a feed capacity of` 10,000 bbls./day of the gasoil feed. The catalyst for this operation consisted of an activated clayknown commercially as Super-Filtrol in a fine- 1y divided or powderedcondition, that is, of a fneness suicient to pass a 100 mesh screen andconsisting largely of particles of indiscriminately mixed sizes smallerthan 100 microns in average diameter.

Table A Gas `oil feed, bbls./day` 10,000 Steam feed, lbs./hr. 13,000Reactor dimensions, (a) length, ft 50 Reactor dimensions., (b) diameter,ft 12 Feed weight ratio of "catalyst to oil 5 "The regenerationoperation is preferably effected in accordance with the same principlesas the conversion stage, except that in the latter case the gaseouscomponent contacted with the catalytic particles consist of anoxygen-containing gas such as air. Also, in the regeneration stage aportion of the regenerated catalyst is preferably recycled to theregeneration zone with intervening cooling of the recycled stream ofcatalyst for the purpose of temperature control within `the regenerationzone. Optionally, a simi-` lar recycle stream of used catalyst may beemployed if desired in connection with reactor 2 with interveningheating if this recycled stream of spent catalyst, or cooling, asdesired for the purpose of temperature control Within the conversionzone or for varying the average degree of catalytic :activity of thecatalyst mass.

Spent catalyst may be suitably introduced into regenerator 3 `bycatalyst standpipe .25 leading directly thereto whereby the transfer `ofcatalyst from the reactor to the regenerator is effected entirely bygravity flow. The enteringstream of spent catalyst particles meets andis intimately mixed With the stream of cooled recycled catalystintroduced through catalyst inlet 26. An oxygen-containing gas,preferably air, is introduced at the base of the regenerator throughmanifold 21 and branch valved lines 2l'. Air is supplied through lines21 in such quantity that the mass of catalyst particles thereabove ismaintained in a freely owable but relatively dense state. In this casesimilar to that prevailing in the conversion zone the mass of relativelydense aerated catalyst resembles a liquid in its flow characteristicsand is positively displaced laterally through the regeneration zone bythe addition of catalyst particles at one end portion and the Withdrawalof catalyst particles at the opposite end portion. i

, The height of the catalystlevel 28 is controlled in accordance withthe same principlesof operation described for level I3, so that underpreferred conditions a relatively small quantity of catalyst particlesis withdrawn overhead with the regeneration gases through regenerationgas outlets 29.

A stripping zone 30 is provided at the catalyst outlet end of theregenerator similar to stripping zone 20 for the purpose of strippingoxygencontaining gases from the regenerated catalyst. A suitablestripping medium such as steam `is supplied to zone 30 through line 3land distributing means 32.

The regenerated catalyst is withdrawn in two separate streams throughcatalyst standpipe`s33 and 34. Standpipes 33 and 34 may each be providedat the upper end portion thereof With`an enlarged section 35 and 36,respectively', similar to I4 and provided with means 31 and 3&8 forintroducing a stripping gas thereto. Standpipes 33 and 34 are furtherprovided with lines139 and 40, respectively, spaced at suitable pointsalong their length for introducing steam or other aerating medium tomaintain the catalyst therein in a freely ilowable condition.

From valve 39 in catalyst standpipe 34 regenerated catalyst is forwardedto the conversion zone through transfer line I 0 as previouslydescribed. From catalyst standpipe 33, the 'quantity of regeneratedcatalyst withdrawn is that required for temperature control within theregeneration zone 3. Dependent upon the type of catalyst or contactmaterial employed there is nor mally a maximum regeneration temperaturewhich should not be exceeded, for example in the case of a crackingcatalyst consisting of an activated clay of the Super-Filtrol typethistemperature is normally taken as about 1100 to 1150 F.

Recycled catalyst is fed by valve 40 from catalyst standpipe 33 into astream of a conveying fluid, suitably `air derived from compressor 4,through line 4I and passed by line 42 through a heat exchanger 43through which a cooling medium is circulated by lines 44 and 45. Inexchanger 43 the stream of recycled catalyst is cooled to a temperatureadapted to provide the desired temperature control during theregeneration operation. A balile 4B may be provided at the outlet ofcatalyst inlet 26 to subserve the same purpose as baffle I2.

Gaseous combustion products are withdrawn overhead from regenerator 3through outlets `29 and are passed to a. suitable gas-solids separatingsystem to separate catalyst particles suspended therein. The quantity ofcatalyst carried overhead,`as in the case of the reaction zone, ispreferably maintained at a relative low amount thereby greatlysimplifying the recovery system necessary for the separation of thismaterial from the gas component. The stripping medium and stripped gasesexiting from zone 30 may suitably be combined with the eilluent gas fromoutlets 29 by line 41. The effluent regeneration gas may be passedlthrough a cooler or heat exchanger 48 prior to passage to the gas-solidsseparating system, although this cooling step may optionally be omitted.From heat exchanger 48 the gas mixture passes by line 49 to a suitablegas-solids separator such as a Cottrell precipitator, a cycloneseparator, or the like, wherein the small quantity of suspended solidsmay be suitably separated. In lseparator 5, the flue gas is withdrawnoverhead through line 50 and the separated solids are withdrawn at thebottom through hopper 5l. Any required amount of make up catalyst may besupplied to hopper 5l from fresh catalyst hop-per I6. v From hopper 5Ithe recovered catalyst is returned by catalyst standpipe 52 to theregenerator'by transfer line 53 to which a suitable conveying fluid suchas steam is supplied by line 54.

Operating conditions suitably maintained in the regeneration stage ofthe process are illustrated by the conditions tabulated in the appendedTable B for a regeneration operation corresponding to the conversionoperation given in Table A.

Table B spent catalyst, lbs/hr 632,840 Cooled recycled catalyst, llos/hr900,000 Ratio by weight recycled to spent catl alyst A1.43 Inlettemperature, spent catalyst, F 900 Inlet temperature, recycled catalyst,F 700 Outlet temperature of c at a l y s t and gas, F 1,000 Regeneratordimensions: l

(a) Length, ft 72 (b) Diameter, ft 20 Regenerator gas velocity, ft./sec0.5

Air feed, lbs/hr 91,000 Catalyst concentration:

(a) Regenerator, lbs/cu. ft 23 (b) Outlet gas, grains/ cu. ft 20 Weightpercent of coke produced based on oil feed 5.0 Coke percent .by weighton spent catalyst 1.3 Carbon percent by weight on regenerated v catalyst0.7 Catalyst contact time, seconds 615 Pressure in regenerator, lbs/sq.in '7 Horizontal catalyst velocity, ft./sec 0.12

Certain variable operating conditions in the practice of the process mayfollow and be controlled pursuant to conventional practice in the artwith respect to the particular conversion or treating reaction involved.For example in the application of the process to the vapor phasecatalytic cracking of high boiling hydrocarbons to low boilinghydrocarbons within the motor fuel boiling range, such factors as theselection of suitable charging stock, catalytic material, conversiontemperatures, pressures, and the like, may be determined in accordancewith conventional practice in this particular art.

The rate of fresh catalyst feed is dependent upon the desired averagecatalytic activity of the dense phase of catalyst in the conversionzone, and fresh catalyst is continually added at a rate adapted tomaintain such activity at the desired value as the conversion proceeds.Used catalyst is withdrawn at the same average rate as fresh catalyst isadded, therefore, the average time a catalyst particle remains in thereactor (catalyst residence time) is determined by the catalyst feedrate and may be calculated by dividing the Weight of catalyst in thereactor by the catalyst feed rate per minute. Y

The weight of catalyst in the reactor is depend ent upon theconcentration of the dense phase and the height of the upper level ofthis phase. In the application of the process to the catalytic crackingof high boiling hydrocarbons it is preferred to maintain the ratio ofthe weight of oil fed per hour to the weight of catalyst in the reactionzone (w./hr./W.) within the range of about 1.0 to 25.0 and preferablywithin the more restricted range of about 2.5 to 10.0. Also, in thiscase it is preferred to utilize a catalyst to oil feed rate ratio withinthe range of 0.5:1 to 20:1 and preferably within the more restrictedrange of The velocity of the gaseous component preferably maintained inthe practice of the process is dependent upon the character of thecatalytic particles employed with respect to such factors as theirindividual size, shape and density. The gaseous component should bemaintained at a velocity of sufcient magnitude to aerate the mass ofcatalyst particles to an extent sufficient to maintain them in a readilyflowable condition. Further, the maximum velocity must not be in excessof that velocity below which a relatively dense or concentrated phase ofthe catalyst particles is produced in the solids-vapor contact zone. Atrelatively high vertical gasv velocities the catalyst particles may besuspended in the stream of gas and carried along therewith at a velocityapproaching that of the gas particles. At relatively low vertical gasvelocities the effect of the phenomenon known as "slip becomespronounced and in the zone of such low velocities the solid catalyticparticles accumulate, thereby producing a relatively dense orconcentrated phase. In the practice of the present process lateralinternal recycle is avoided. The avoidance of such recycling isprovidedby the horizontally elongated configuration of the conversion andregeneration zones, and the relative thinness of the bed ofI catalystcompared to its length. Under these conditions, it is apparent that thecarbonaceous content of the laterally moving bed is progressivelyincreased in the direction of flow in the conversion zone, and that theconverse is true in the regeneration zone. Accordingly, the quantitiesof the gaseous component admitted through each of the valved lines, 6and 21 may be adjusted with respect to the carbon concentration of thecatalyst above the individual gas inlets.

Since reactor 2 and regenerator 3 are of uniform diameter the averagelateral velocity of the particles therethrough will be substantiallyuniform. This velocity may be varied toadvantage in certain instances bymodifying the cross-sectional area in various parts of the reactionvessel, for example, by gradually increasing this area in the directionof lateral flow the velocity of the catalyst particles will beprogressively lower in the direction of flow. Likewise the thickness ofthe catalyst bed may be varied in different parts of the reaction zoneby suitably contouring the bottom of the reaction vessel. This sameeffect may also be produced by inclining the reaction vessel whereby thebed will be so disposed that it gradually increases or decreases inthickness in the direction of ow dependent upon whether the inlet end ofthe reaction vessel is made higher or lower than the outlet end.

Any of the various known types of cracking catalyst may be utilized inthe practice of the invention. The preferred catalysts are those of thesilica-alumina, or silica-magnesia type adapted to produce asatisfactory yield of high octane gasoline. Either silica-aluminacatalyst consisting of activated clay prepared by the acid treatment ofnatural clays, for example the commercial product Super-Filtrol or asynthetically prepared silica-alumina catalyst such as those disclosedin copending applications of Robert Ruthruir', Serial Nos. 305,472 nowU. S.

Patent 2,391,481 and 305,473 now U. S. Patent 2,391,482, both filedNovember 2l, 1939, may be employed. The catalyst is preferably employedin iinely divided or powdered condition, for example with particlesranging from about l to 100 microns. However, :granular catalystparticles may be employed, and in this instance a mixture of granularand powdered catalytic material is preferred.`

Pursuant to the preferred embodiment of the invention, the conversionzone and the regeneration zone are `maintained under substantially thesame pressure that is 7 lbs/sq. in each as set forth in Tables A and B.The maintenance of this condition has the important advantage ofminimizing the application of pressure and the height of standpipes- 25and 34 necessary to transfer catalyst in the cyclic circulation betweenthe zones. The arrangement of one of the zones at a diiferent horizontallevel than the other zone interconnected directly by a standpipe 25`provides for direct gravity ow of the catalyst without the necessity ofproviding a carrier line in which the catalyst is carried in suspension.A further feature of the iiow illustrated is the use of a non-reactivegas, for example steam in carrier line lll to transfer the catalystbetween the zones independently of the now of reactant gas and vapors.Standpipe 25 similarly may be arranged to discharge into a carrier linesimilar to line H) and the reactor and regenerator thereby placed on thesame horizontal level or in a cornmon housing. The flow of purging gas.,particularly steam through zone 20 in parallel ilow with the hydrocarbonvapors in reactor 2, is especially advantageous in its avoidance ofintermingling of the purging fluid with the catalyst in zone 2 andconsequent acceleration in catalyst deactivation. These and similarfeatures, both individually and in combination, are important featuresof our process and are the subject of the following claims.

I claim:

1. In a process for contacting solids and gases by passing said gasesupwardly through a mass of said solids in iinely-divided form in areaction zone at a velocity such that said mass of solids are maintainedin a state of separation into a lower dense phase resembling a liquid inits iiow characteristics, and an upper dilute phase of substantiallylower solids concentration, an improved method of introducing andflowing said solids through said reaction zone which includes the stepsof: upwardly introducing a confined stream of solids suspended in gasesinto said reaction zone at an elevation above the surface of said densephase; deflecting said upwardly introduced stream downwardly onto anupper surface oi' said dense phase; flowing said dense phase masssubstantially horizontally away` from said point of introduction to apoint of withdrawal of dense phase solids; withdrawing eiiiuent vaporsfrom said reaction zone from said dilute phase therein at a point abovesaid point of deflection of said incoming stream.

2. In a catalytic conversion system of the iluidized catalyst type,wherein the reactant vapors are passed upwardly through a mass ofcatalyst in a reaction zone at a velocity adapted to maintain said massin a dense flowable liquid-simulating condition, and wherein spentcatalyst is continuously withdrawn from said reaction zone andregenerated in separate regeneration zone, an improved method forwithdrawing and stripping spent catalyst from said reaction zone whichmethod includes the steps of: flowing catalyst in a liquid-simulatingcondition from said reaction zone dense phase through a restrictedopening, communicating directly and exclusively with the dense mass ofcatalyst in the reaction zone and into a stripping-zone separate fromsaid reaction zone dense phase; stripping residual vapors from saidwithdrawn catalyst in by means of stripping gas; withdrawing thevaporous products from said reaction zone dense phase; withdrawingstripping gases and stripped vapors from said stripping-zone; andcombining said vaporous products withdrawn from said reaction zone densephase and said stripped gases withdrawn from said stripping zone densephase.

3. A method of contacting solid particles and gaseous duid whichcomprises introducing subdivided solid particles and gaseous iiuid intoa contacting zone and maintaining the particles as a fluidized denseliquid-simulating mixture in said reaction zone, withdrawing denseluidized solid particle mixture from the lower portion of saidcontacting zone and passing it to the bottom of a separate strippingzone, introducing stripping gas into the lower portion of said strippingzone at a velocity selected to maintain the particles in a densefiuidized liquid-simulating condition during stripping, removingstripped particles from the bottom portion of said stripping zone in a`dense iluidized condition and removing stripping gas and stripped-outconstituents from the upper portion of said stripping zone.

4. A method according to claim 3 wherein the gaseous fluid contains onlya small amount of entrained catalyst in the upper portion of saidcontacting zone and the stripping gas from the top of said strippingzone is combined directly with the gaseous fluid withdrawn from theupper part of said contacting zone above the dense mixture.

5. A method according to claim 3 wherein the gaseous fluid contains onlya small amount of entrained catalyst in the upper portion of saidcontacting zone and the stripping gas from the top of said strippingzone is combined with said gaseous fluid containing only a small amountof entrained catalyst.

5. In a method of contacting solid particles and a gaseous uid in acontacting zone wherein the particles are maintained as a dry denseliquidsimulating mixture, the improvement which comprises passing thedry dense mixture from the bottom portion of said contacting zone to thebottom portion of a separate stripping zone to remove entrained gaseousiiuid and wherein the particles are maintained as a dense iiuidizedmixture, introducing stripping gas into the bottom portion of saidstripping zone and withdrawing ydense iiuidized stripped contactparticles from the. bottom portion of said stripping zone andwithdrawing stripping gas together with strip-nedout constituents fromthe upper portion of said stripping zone.

'7. In a catalytic conversion system nf the. fluidiynd. nai-,alv/:t-vria wherein reactant V'ahf'ws 2,179, pageed unwavdlv through a, massof natalvst in a reaction zope at a velonitv adapted tn maintain saidmass in a, stai-.Q nf senaratinn into a lower dence, phase in a.flmvahle. Hemd-simulatl'lU nnhfitfin QYifl 911 Tinley filn-n ribose 0fS1111- stapt-5911i? natalvc, mi wher-pin crient nato'vef, isnmntinnnuelv mii-hf-lv-awn from said reaction zone and regenerated in a`separate regeneration zone. an improved method for withdrawing andstripping spent catalyst from said reaction zone. which method ,includesthe steps of: flowing dense phase catalyst in a uniud-simulatingcondition from below the surface of said reaction zone dense phase.through a restricted opening, and into a stripping-zone dense phase.below the surface thereof. said stripping-zone dense phase beingmaintained in a stripping zone distinct from said reaction zone. butcommunicating therewith by means of said restricted opening connectingthe dense phases of the two zones; introducing stripping gases upwardlythrough said stripping zone at a velocity adapted to maintain catalysttherein in a state of separation into a stripping-zone dense phase andan upper dilute phase of substantially reduced catalyst concentration,said stripping-zone and reaction-zone dilute phases being maintainedseparately from one another in said stripping zone and said reactionzone respectively; separately withdrawing vapors from said reaction zoneand said stripping zone from their respective dilute phase regions; andwithdrawing catalyst from the lower portion of said strippingzone densephase for transfer to said regeneration zone.

8. In a catalytic conversion system of the fluidized catalyst type,wherein reactant vapors are passed upwardly through a mass of catalystin a reaction zone at a velocity adapted to maintain said mass in astate of separation into a lower dense phase in a fiowableliquid-simulating condition and an upper dilute phase of substantiallylower catalyst concentration, and wherein spent catalyst is continuouslywithdrawn from said reaction zone and regenerated in a separateregeneration zone, an improved method for withdrawing and strippingspent catalyst from said reaction zone, which method includes the stepsof: continuously flowing a part of said reactionzone dense phasesubstantially horizontally through a restricted opening below thesurface of said dense phase into a stripping zone out of the path ofsaid vapors; introducing stripping gases upwardly through said strippingzone at a velocity adapted to maintain catalyst therein in a state ofseparation into a stripping-zone dense phase and an upper dilute phaseof substantially reduced catalyst concentration, said strippingzone andreaction-zone dilute phases being maintained separately from one anotherin said stripping zone and said reaction zone respectively; separatelywithdrawing vapors from said reaction zone and said stripping zone fromtheir respective dilute phase regions; and withdrawing catalyst from thelower portion of said strippingzone dense phase for transfer to saidregeneration zone.

9. In a catalytic conversion system of the uidized catalyst type,wherein reactant vapors are passed upwardly through a mass of catalystin a reaction zone at a velocity adapted to maintain said mass in astate of separation into a lower dense phase in a nowableliquid-simulating condition and an upper dilute phase of substantiallylower catalyst concentration, and wherein spent catalyst is continuouslywithdrawn from said reaction zone and regenerated in a separateregeneration zone, an improved method for withdrawing and strippingspent catalyst from said reaction zone, which method includes the stepsof flowing dense phase catalyst in a liquid-simulating condition frombelow the surface of said reaction zone dense phase, through arestricted opening, and into a stripping-zone dense phase, below thesurface thereof, said stripping-zone dense phase being maintained in astripping zone distinct from said reaction zone, but communieatingtherewith by means of said restricted opening connecting the densephases of the two zones; introducing stripping gases upwardly throughsaid stripping zone at a velocity adapted to maintain catalyst thereinin a state of separation into a stripping-zone dense phase and an upperdilute phase of substantially reduced catalyst concentration, saidstripping-zone and reaction-zone dilute phases being maintainedseparately from one another in said stripping zone and said reactionzone respectively; Vseparately withdrawing vapors from said reactionzone and said stripping zone from their respective dilute phase regions;downwardly withdrawing a dense iiowable column increasing in pressure inthe direction of flow from the lower portion of said stripping-zonedense phase; and transferring catalyst from the base of said column tosaid regeneration zone.

10. In a catalytic conversion system of the fiuidized catalyst type,wherein reactant vapors are passed upwardly through a mass of catalystin a reaction zone at a velocity adapted to maintain said mass in astate of separation into a lower dense phase in a iiowableliquid-simulating condition and an upper dilute phase of substantiallylower catalyst concentration, and wherein spent catalyst is continuouslywithdrawn from said reaction zone and regenerated in a separateregeneration zone, an improved method for withdrawing and strippingspent catalyst from said reaction zone, which method includes the stepsof: ilowing dense phase catalyst in a liquid-simulating condition frombelow the surface of said reaction zone dense phase, through arestricted opening, and into a stripping-zone distinct from saidreaction zone and communicating therewith only by means of saidrestricted opening for discharging spent catalyst from said reactionzone into said. stripping zone; introducing stripping gases upwardlythrough said stripping zone at a velocity adapted to maintain catalysttherein in a state of separation into a stripping-zone dense phase andan upper dilute phase of substantially reduced catalyst concentration,said strippingzone and reaction-zone dilute phases being maintainedseparately from one another in said stripping zone and said reactionzone respectively; separately withdrawing vapors from said reaction zoneand said stripping zone from their re` spective dilute phase regions ofsaid reaction zone and said stripping zone are then combined and passedto centrifugal gas-solid separating means for recovery of residualentrained solids.

12. In a catalytic conversion system of the fluidized catalyst type,wherein reactant vapors are passed upwardly through a mass of catalystin a reaction zone at a velocity adapted to maintain said mass in astate of separation into a lower dense phase in a flowableliquid-simulating condition and an upper dilute phase of substantiallylower catalyst concentration, and wherein spent catalyst is continuouslywithdrawn from said reaction zone and regenerated in a separateregeneration zone, an improved method for withdrawing and strippingspent catalyst from said reaction zone, which method includes the stepsof: ilowing dense phase catalyst in a liquid-simulating condition frombelow the surface of said reaction Zone dense phase, through arestricted opening, and into a stripping zone separate and distinct fromsaid reaction zone; introducing 1 stripping gases upwardly through saidstrippingzone at a velocity adapted to maintain catalyst therein in astate of separation into a strippingzone dense phase and an upper dilutephase of substantially reducedcatalyst concentration, saidstripping-zone and reaction-zone dilute phases being maintainedseparately from one another in said stripping zone and said reactionzone respec tively; ilowing vapors upwardly from said reaction-zone`dense phase and said stripping-Zone `dense phase through the separatedilute phase regions above said respective dense phases; combiningvapors being withdrawn from the upper part of said reaction-zone andsaid stripping-zone dilute phase regions; and withdrawing catalyst fromthe lower portion of said stripping-zone dense phase in a llowableliquid-simulating condition and an upper dilute phase of substantiallylower catalyst concentration, and wherein spent catalyst is continuouslywithdrawn from said reaction zone and regenerated in a separateregeneration zone, an improved method for withdrawing and strippingspent catalyst from said reaction zone, which method includes the stepsof continuously flowing a part of said reaction-zone dense phaselaterally through a restricted opening below the surface of said densephase out of said dense phase and into a stripping zone out of the pathof said vapors; introducing stripping gases upwardly through saidstripping zone at a velocity adapted to maintain catalyst therein in astate of separation into a stripping-zone dense phase and an upperdilute phase of `substantially reduced catalyst concentration, saiddense phase for transfer to said regeneration zone.

` 13. In a catalytic conversion system of the uidized catalyst type,wherein the reactant vapors are passed upwardly through a mass ofcatalyst in a reaction zone at a velocity adaptedl to maintain said massin a state of separation into a lower dense phase in a flowableliquid-simulating condition and an upper dilute phase of substantiallylower catalyst concentration, and wherein spent catalyst is continuouslywithdrawn from said reaction zone and regenerated in a separateregeneration zone, an improved method for withdrawing and strippingspent catalyst from said reaction zone which method includes the stepsof: flowing dense phase catalyst in a liquid-simulating condition fromsaid reaction zone dense phase, through a restricted opening below thesurface of said densephase and into a stripping zone separate from said`reaction zone dense phase and said reactant vapors; stripping residualvapors from said withdrawn catalyst by passing stripping gas upwardlythrough said catalyst` in said stripping zone; withdrawing the vaporousproducts from said reaction zone dense phase; separately withdrawingstripping gases and stripped vapors from said stripping zone; combiningsaid vaporous products withdrawn from said reaction zone dense phase andsaid stripped gases withdrawn from said stripping zone dense phase;withdrawing catalyst from said stripping zone for transfer to saidregeneration zone.

14. In a catalytic conversion system of the iluidized catalyst type,wherein reactant vapors are passed upwardly through a mass of catalystin a reaction zone at a velocity adapted to maintain said mass in astate of separation into a lower stripping-zone dilute phase beingmaintained separately from said reaction zone; flowing vapors upwardlyfrom said reaction-zone dense phase and said stripping-zone dense phasethrough separate dilute phase regions above said respective densephases; combining vapors being withdrawn from the upper part of saidreactionzone and said stripping-zone dilute phase regions; andwithdrawing catalyst from the lower portion of said stripping-zone densephase for transfer to said regeneration zone.

15. In a catalytic conversion system of the fluidized catalyst type,wherein reactant vapors are passed upwardly through a mass of catalystin a reaction zone at a velocity adapted to maintain said mass in astate of separation into a lower dense phase in a flowableliquid-simulating condition and an upper dilute phase of substantiallylower catalyst concentration, and wherein spent catalyst is continuouslywithdrawn from said reaction Zone and regenerated in a separateregeneration zone, an improved method for withdrawing and strippingspent catalyst from said reaction zone, which method includes the stepsof: ilowing catalyst in said dense condition from said reaction zonedense phase below the surface thereof through a restricted opening intoa stripping zone separate and distinct from said reaction zone;introducing stripping gases upwardly through said stripping zone at avelocity adapted to maintain catalyst therein in a state of separationinto a stripping-zone dense phase and an upper dilute phase ofsubstantially reduced catalyst concentration; maintaining saidstripping-zone dilute phase separate from said reaction zone to settleentrained particles from stripping vapors without recontacting saidsettling particles with reaction vapor; flowing vapors upwardly fromsaid reaction-zone dense phase and said stripping-zone dense phasethrough separate dilute phase regions above said respective densephases; combining vapors being withdrawn from the upper part of saidreaction-zone and said stripping-zone dilute phase regions; and

withdrawing catalyst from the lower portion of' said stripping-zonedense phase for transfer to said regeneration zone.

References Cited in the file of this patent UNITED STATES PATENTS Keithet al. July 18, 1950

3. A METHOD OF CONTACTING SOLID PARTICLES AND GASEOUS FLUID WHICHCOMPRISES INTRODUCING SUBDIVIDED SOLID PARTICLES AND GASEOUS FLUID INTOA CONTACTING ZONE AND MAINTAINING THE PARTICLES AS A FLUIDIZED DENSELIQUID-SIMULATING MIXTURE IN SAID REACTION ZONE, WITHDRAWING DENSEFLUIDIZED SOLID PARTICLE MIXTURE FROM THE LOWER PORTION OF SAIDCONTACTING ZONE AND PASSING IT TO THE BOTTOM OF A SEPARATE STRIPPINGZONE, INTRODUCING STRIPPING GAS INTO THE LOWER PORTION OF SAID STRIPPINGZONE AT A VELOCITY SELECTED TO MAINTAIN THE PAR-